Loremapper is a free, open-source fantasy map editor for worldbuilding and tabletop campaigns such as D&D. Generate a fantasy continent from a seed, sculpt terrain, paint forests and deserts, draw rivers, roads and kingdoms, and place castles, cities and your own artwork. Maps stay in your browser; no account is needed.
The editor needs JavaScript and WebGL 2. Source code: github.com/mercurial20/loremapper